Field of the Invention
The present invention relates to a method of manufacturing a solid-state image sensor.
Description of the Related Art
A solid-state image sensor includes, for example, a substrate including a photoelectric conversion portion, an insulating member arranged on the substrate, and a light-guide portion arranged in the insulating member and on the photoelectric conversion portion. The light-guide portion guides incident light to the photoelectric conversion portion by reflection. The light-guide portion is formed by, for example, forming the insulating member on the substrate, and then forming an opening in the insulating member and filling the opening with a translucent member having a higher refractive index than that of the insulating member.
Japanese Patent Laid-Open No. 2008-103757 discloses a structure in which an inclined angle of a side face of the upper part in a light-guide portion (an angle formed by the side face and the upper face of a substrate) is smaller than an inclined angle of a side face of the lower part in the light-guide portion. According to Japanese Patent Laid-Open No. 2008-103757, after an insulating member is formed on the substrate, a resist pattern having an opening is formed on the insulating member and the first etching as isotropic etching is performed on the insulating member by using the resist pattern as a mask. Consequently, an opening having an inclined side face is formed in the upper part in the insulating member. Then, the second etching as anisotropic etching is further performed on the insulating member in which the opening has been formed by using this resist pattern as the mask. By such a procedure, an opening for the light-guide portion is formed such that an inclined angle of a side face of the upper part in the opening becomes smaller than an inclined angle of a side face of the lower part. According to a method in Japanese Patent Laid-Open No. 2008-103757, a void is hardly generated in the light-guide portion when the light-guide portion is formed by filling the opening with a translucent member.
According to the method in Japanese Patent Laid-Open No. 2008-103757, however, the shape of the side face (inclined side face) of the opening formed by the first etching may change in the second etching and the shape of the opening for the light-guide portion obtained after the second etching may deviate from a desired shape. Therefore, in the light-guide portion obtained by filling the opening with the translucent member, a light collection amount may decrease by decreasing the upper diameter of the light-guide portion or incident light may not be reflected properly toward the photoelectric conversion portion. This may cause a decrease in the light collection characteristic of the light-guide portion.